Combi-3: Home CNC Mill

This desktop sized mill can be 2, 3 or 4 axis CNC. It is very useful in basic 2-axis CNC or XY configuration. The photo M1 shows the machine which is the Sieg X1 converted by adding direct drive stepping motors to the X and Y leadscrews.

In XY mode the machine will cut all shapework for clocks in batches of Plates, Pallet, Click and Spring, Back cock, Winding cock and with a simple manual indexer can cut all wheels, pinions, escape and ratchet as shown in the photo M2 skeleton clock.

Even the Roman numerals are easily possible requiring just 43 manual UP and DOWN moves which are prompted for by the program. All machining was with the standard Sieg cutter head with 2000rpm max spindle speed. This is fine for profiling but too slow for engraving. Once engraving uses TrueType fonts there is no scope for manual Z-axis moves as the data sets get very large with lots of cutter UP / DOWN required.

The clock pallet was profile milled from 3mm gauge plate with a 1.5mm diameter cutter. For example, if the design of the recoil escapement is studied and understood then producing a data set which allows the pallet to be cut, hardened, polished, mounted and fitted into the clock with no further work required is a very satisfying milestone which says "2-D CNC, you can do it".

When driving the Z-axis through CNC the head casting is always locked to the vertical column with the motion being through the quill. The quill is moved through the standard rack and pinion shaft by geared shaft from behind the head (photo M4).

Configurations and typical use:

• Clock making: XY CNC with Sieg cutter head and manual Z-axis, photo M6 shows the XY cutting clock plates in 5mm brass with 2mm endmill
• Model making: XYZ CNC with Sieg cutter head, Z-axis driven by gears to pinion shaft (photo M4)
• Instrument making: XYZ CNC with remote cutter motor driving through industrial 6mm flex drive to spindle in balanced quill, Z-axis driven by leadscrew
• PCB drilling/routing: XYZ CNC with turbine/spindle under a balanced quill, Z-axis drive can be any of the above, belt drive is recommended photo M9
• XYZA CNC photo M7 shows a typical 'fourth axis' device, in this case a stepper powered rotary table, but could be a dividing head as shown in photo M8, or other job specific fixture.